Temperature dependence of elastic properties in austenite and martensite of Ni-Mn-Ga epitaxial films

0489353 - FZÚ 2019 RIV GB eng J - Journal Article
Heczko, Oleg - Seiner, Hanuš - Stoklasová, Pavla - Sedlák, Petr - Sermeus, J. - Glorieux, C. - Backen, A. - Fähler, S. - Landa, Michal
Temperature dependence of elastic properties in austenite and martensite of Ni-Mn-Ga epitaxial films.
Acta Materialia. Roč. 145, Feb (2018), s. 298-305. ISSN 1359-6454. E-ISSN 1873-2453
R&D Projects: GA ČR GA17-00062S
Institutional support: RVO:68378271 ; RVO:61388998
Keywords : magnetic shape memory alloys * elastic properties * surface acoustic waves * Ni₂MnGa * NiMnGa
OECD category: Condensed matter physics (including formerly solid state physics, supercond.); Acoustics (UT-L)
Impact factor: 7.293, year: 2018

Using surface acoustic waves (SAW) the elastic properties of 500 nm thick epitaxial off-stoichiometric Ni-Mn-Ga films prepared by sputtering on MgO substrate were determined in a broad temperature range both in austenite and martensite and across the martensitic transformation. At room temperature the films were in non-modulated martensite with tweed-like microstructure. Structural and magnetic studies proved that the martensitic structure can be considered homogenous on the scale of surface waves owing to the fine twinning. Measured angular dependence of SAW velocities indicated that the averaged in-plane tetragonal structure can be used for the calculation of elastic coefficients in martensite. The phase velocity of SAW showed an anomaly around the phase transition temperature due to changes of the shear elastic coefficients, c'and c(44). During cooling there was a gradual softening of c' in austenite.
Permanent Link: http://hdl.handle.net/11104/0283786